Risk
ESD.864
Noelle Selin
April 2 and 9, 2013
1
What is risk?
 Risk = hazard x probability
 Degree of harm x likelihood of harm
 Must use models/technical analyses to
constrain both “degree” and “likelihood”
 Risk assessment frameworks:
assessment/decision-making processes
on risks
2
Risk as an assessment
framework
 Risk vs. Risk
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From Slovic, “Beyond Numbers”
3
© Westview Press. All rights reserved. This content is excluded from our Creative Commons
license. For more information, see http://ocw.mit.edu/help/faq-fair-use/.
Source: Slovic, Paul, Baruch Fischhoff, et al. "Characterizing Perceived Risk." R. W. Kates, C. Hohenemser, &
J. X. Kasperson (eds.), Perilous progress: Managing the Hazards of Technology, pp. 91-125, Westview, 1985.
4
Slovic et al 1985
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5
Risk as a decision tool
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Zero risk (no animal carcinogens in food)
De minimis risk (<10-6 lifetime risk of cancer)
Safety (no observable effect level)
Acceptable risk (regulatory policy standard)
Risk tradeoffs
 risks vs. benefits (economic, social)
 risks vs. risks (flying vs. driving)
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Traditional Risk Analysis: Steps

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Research
Hazard identification
Exposure assessment
Risk characterization
Risk communication
Risk management
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National Research Council, “Red Book”
Model of Risk Analysis (1983)
Research
Risk Management
Risk Assessment
Laboratory and
field observations
Information on
extrapolation methods
Development of
regulatory option
Toxicity assessment :
Hazard identification
and close-response
assessment
Evaluation of public
health, economic,
social, political
consequences
of regulatory options
Research needs identified
from risk assessment
process
Field measurements,
characterization of
populations
Risk characterization
Exposure assessment
emissions characterization
Agency decisions and
actions
Image by MIT OpenCourseWare.
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Issues raised by traditional
risk-based approaches
 Framing of the problem
 Uncertainty…and ignorance?
 Different sorts of expertise; lay public
input
 Separation of risk assessment, risk
management functions
 Conservative bias?
 Risk vs. risk considerations?
9
Build-your-own risk assessment
model
 Imagine an assessment process for a new and
potentially hazardous chemical (let’s say it’s a
pesticide). With reference to the NRC 1983 risk
diagram, construct your own risk-assessment
model which would address some of the criticisms
of that model. You might think about:
 How something is selected for risk analysis
 Feedbacks from the process?
 Role of the public in defining risks, risk
communication, etc.
 Conceptual separation between risk
assessment/risk management
 Any changes to steps?
10
MIT OpenCourseWare
http://ocw.mit.edu
ESD.864 / 12.844J Modeling and Assessment for Policy
Spring 2013
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